Process and apparatus for producing abrasive material



Sept. 26, 1950 o. s. STEWART 2,523,454

PROCESS AND APPARATUS FOR PRODUCING ABRASIVE MATERIAL Filed May 15, 1946 Patented Sept. 26, 1950 UNITED STATES PATIENT OFFICE PROCESS AND APPARATUS FOR PRODUC- ING ,ABRASINE MATERIAL Orald S. Stewart, Cleveland, Ohio Application May 15, 1946, SerialNo. 670,004 4 Claims. (01. l8-2.5)

This invention relates to the manufacture of abrasive material and more particularly to the manufacture of that type of such material as is known to the trade as shot and which is utilized for blasting metal surfaces for cleaning and other purposes.

It is a general purpose and object of the invention to enable the shot to be produced economically and efliciently in desired variations of sizes wherein the particles will be not only spherical in shape but solid throughout their extent.

I accomplish the foregoing objects by employing a special composition of gray cast iron and by subjecting this iron while in a molten state to a. special treatment, preferably by the use of an apparatus of the type shown in the drawings hereof, wherein Fig. 1 represents a somewhat diagrammatic illustration, in sectional side elevation, of an apparatus by means of which my invention can be realized, in conjunction with a particular composition of molten gray iron; Fig. 2 is a plan 'viewof the apparatu shown in Fig. 1; and Fig. 3 is a front elevational view, on an enlarged scale, of the aforesaid apparatus, parts being broken away.

In practicing my invention, I insure a suflicient degree of fluidity in the molten metal used in the production of the shot by employing, for the metal to be melted, a gray cast iron having a silicon content of from 1 to 3%. By using an iron of this composition, I am enabled, by the operation of my apparatus, to break up a molten stream of such iron into shot which are not only spherical but which are solid throughout, as distinguished from being objectionably hollow. Where the silicon content of the iron is materially lower than the lower limit specified, the molten streams of such iron will not be broken up into spherical solid shot by the operation of my apparatus, it being noted that the presence of silicon in the iron in the proportions specified renders the resultant molten metal sufiici'ently fluid at temperatures of from 2500 F. to 2700 F., to enable the particles of the same to assume the necessary spherical shape when subjected, in such molten condition, to the action of an air blast supplied by my apparatus.

While I prefer to use silicon in the proportions specified to secure the necessary fluidity in the molten iron, other substances or elements may be employed therewith to accomplish this object.

In the drawings, which are somewhat diagrammatic, Ill denotes generally a receptacle, preferably in the form of a large trough and having a front wall H provided with laterally spaced /-shaped notches i l extending downwardly from the top thereof, a bottom wall .12, ,a rear wall 13 and end walls Ill, the end .walls being shown ,as extending above the front andrear walls and having an opening [5 therein for the reception of the longer pintle leg l6 of a looped support, the shorter leg ll being parallel with theleg l6 and both of said legs being adapted to be received within adjacent openings l8 located fin uprights l9 projecting from ,aJDase 1.9 and, by which the trough can be vertically adjustable .along the said uprights.

denotes the trunk of a centrifugal blower, the fan of which is driven by the shaft 22 of an electric motor 2]. This, trunk is provided with a valve 23 .of any suitable construction, a ate Valve being shown for purposes of illustration. It

' is also provided with a pressure gauge 24 -interposed between the said valve and the nozzle 25, which is located belowthe receptacle l0. nozzle, as will appear by reference to the ,drawing, is approximately twice the width of thetrunk 2'9, and is provided with a narrow discharge slot 26 located below and rearwardly of the notches ,-In operation, air will be delivered through the slot 26 :under pressure varying :from 4 to 5 oz. per square inch, dependent upon the size of shot desired to be produced, and the molten metal will be delivered into this blast of air in streams from the notches I l The receptacle can be tilted about its pintles tofacilitate its delivery into the air blast, or molten metal can be supplied to said receptacle continuously through a conduit 21 and will overflow through the notches.

The receptacle ll! will usuall be supported above the nozzle at a distance which will enable the stream of molten metal-to drop a distance of from 3 inches to 8 inches before encountering the air blast, it being noted that the shorter the distance through which the molten stream is dropped before encountering the blast, the finer will be the resultant shot. This follows from the fact that, where the distance is short, the streams will not have had sufficient time to attain a high velocity before encountering the air blast, and the portions of the streams passing through such blast will be subjected to a longer period of exposure thereto than if the distances were greater, with resultant higher velocities and shorter periods of exposure of the streams to the blast.

The manner in which the receptacle I0 is supported enables the distance through which the molten streams drop before encountering the blast to be regulated in accordance with the size of shot to be produced.

The pressure of the air (or other gaseous fluid) delivered through the nozzle 26 will also vary with the fineness of the shot desired; the higher the pressure employed the finer will be the resultant shot.

The provision of the valve 23, with the pressure gauge 24, enables me to subject the fine streams of molten metal delivered through the notches ll to the particular pressures which will result, in connection with the corresponding distances through which the molten streams drop before encountering the blast, in the production of shot of the desired sizes. This variation in pressure can also be accomplished by varying the distances of the streams from the nozzle outlet; and the use of molten iron of high fluidit will enable the shot thus produced to be spherical and solid throughout.

Where air is employed as the gaseous fluid, the action of the air upon the molten iron is to partially decarbonize the same thereby decreasing its hardness and increasing its toughness.

Having thus described my invention, what I claim is:

l. The combination of an air trunk having a nozzle provided with a vertically narrow and laterally wide outlet, and means for forcing air under low pressure through said trunk and outlet, a receptacle for molten metal provided with a series of latterally spaced openings for delivering molten metal therefrom in streams across the fluid delivered from said outlet, said laterally spaced openings being only one row thick in the direction of fluid flow from said outlet, and means for supporting the said receptacle with the said openings above and in front of said outlet, the said trunk being provided with means for controlling the pressure of fluid supplied therethrough and through the said nozzle, the laterally spaced openings being provided by V-shaped notches in the top of a vertically extending wall of the said receptacle and the means for supporting the receptacle being adjustable vertically toward and from the outlet from the nozzle.

2. The process of manufacturing abrasive shot ofvarying sizes comprising the steps of droppin molten iron in a plurality of fine aligned streams into an air blast directed transversely of the paths of movement of said streams, said air blast being normal to the direction of alignment of said streams and serving to break up the molten streams to droplets and to remove carbon from the iron to increase its toughness and decrease its hardness, said air blast being in the form of a wide narrow screen with an air pressure therein of between about 4 to 25 ounces per square inch.

3. The process of manufacturing abrasive shot of varying sizes which comprises dropping molten iron in a plurality of fine aligned streams one stream thick into a blast of air at atmospheric temperature directed transversely of the paths of movement of said streams, and varying the pressures of the air to which the said streams are subjected in accordance with the sizes of shot desired, said air blast being ejected in the form of a wide shallow band, the variation in the pressure of the air being from approximatel 4 to 25 ounces per square inch, and the distances through which the streams drop being from approximately three to eight inches.

4. The process of manufacturing abrasive shot of varying sizes which comprises dropping molten iron in a plurality of fine aligned streams one stream thick into a blast of air directed transversely of the paths of movement of said streams, varying the pressures of the air to which the said streams are subjected in accordance with the sizes of shot desired, said air blast being ejected in the form of a wide shallow band, and retaining the pressure of the air used between approximately 4 to 25 ounces per square inch.

ORALD S. STEWART.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

